Apparatus for the concentration of sulphuric acid



H. PAULING Sept. 3, 1940.

APPARATUS OR THE CGNQENTRATION OF SULPHURIC ACID Filed Nov. 7, 1938 INVENTOR. Hanny Pancia' BY f Patented Sept. 3, 1940 FFE Harry Pauling, Berlin, Germany Application November 7, 15938, Serial No. 239,3l6 in. Germany @ctober l'l', i936 Claims.

For the concentration of sulphuric acid there are employed in general large boilers with attached dephlegniators, in which continuously about tons of concentrated sulphuric acid are 5 kept boiling. The space occupied by the boilers, the diameter of which amounts to about 2.5 meters, is relatively large in comparison to their efciency. A disadvantage also lies in the fact that in the case oi burning through of a boiler large quantities of boiling hot highly concentrated sulphuric acid leak into the combustion chamber and thus the workmen and the operation of the factory are greatly endangered.

According to the present invention the greatest security of operation and a considerably higher eiiciency with considerably less occupation of space are attained in such a manner that with the same output compared with the cu.,- tomary boilers at any time only a little sulphiuic acid takes part in the concentration, which is eiiected in a single tube which is constructed at its lower part as a lm evaporator and in its upper part as a rectiiication device. The eiciency of such tubes in comparison to the boilers is much higher on account oi the fact that the heating surfaces are better utilised. The strength of the wall of the tube is in each case less than that of a boiler and in addition the rate of streaming of the sulphuric acid is greater in a tube than in a boiler. surfaces also entails a considerable economy of material.

The lower portion or the tube, which is constructed as a film evaporator, lies completely within a heated chamber while the rectification portion projects out over the heated chamber in such a manner that at that part a rectiiication oi the sulphuric acid-water vapours rising from the iilm evaporator is rendered possible with the 40 sulphuric acid to be concentrated, which is delivered at the top in the rectiiication portion. The rectification portion is obviously intended to be well insulated; it can ii" desired also be subjected to a gentle heating by the waste gases of the actual heating Zone. In the rectication portion bubble caps or similarly operating devices are arranged.

In order to effect the result that the sulphuric acid streaming out of the rectiiication portion trickles down in a thin layer on the wall of that part of the tube Serving as evaporator, this part, as has already been proposed for sprinkling evaporators, is completely nlled with material in small pieces, for it is a known phenomenon that in a so-called iilling column the liquid, even when The better utilisation oi the heatingl it is delivered at the top in the middle of the tube cross section, after a relatively short streaming distance only streams down the wall in a thin layer. The saine result is obviously also attained by the known arrangement of a plate 5 at the upper end oi the evaporator tube which conducts the sulphuric acid coming from the rectification portion to the Wall.

Since in the concentration oi sulphuric acid sludge may easily be deposited it is suitable in 10 the lower portion of the tube to arrange coaxially a narrower tube which consists of the saine material as the tube lying in the fire chamber, or, since a good heat conductivity of this tube is not necessary, it may be constructed of cheaper re- 15 sistant ceramic material. In the walls of this tube are provided slits or borings which from the exterior inwards are inclined upwards and serve for passing the vapours into the interior of the narrower tube. This interior remains free 20 while the annular chamber formed by the two tubes is iilled with material in srnall pieces.

When the sulphuric vacid to be concentrated is supplied to this intermediate space not continuously but for example for a few seconds every 25 minute, there is produced a socalled liquid plunger which sinks within the filling with a definite velocity in such a manner that it completely fills the intermediate space between the individual small lling elements. Thus a thorough rinsing 30 or" the material in small pieces takes place without the quantity of liquid being increased calculated over a long period.

The individual tubes are at their lower ends, which suitably lie outside the i'ire chamber, pron 35 vided with a closure which collects the concentrated sulphuric acid nowing downwards and from which it is supplied for further use, Whether to a collecting tube or to a separate or common cooler.

The apparatus according to the invention is illustrated in the accompanying drawing. In the drawing Figures l and 2 are illustrations of the apparatus in section elevation, Figures 3 and l in cross section, and Fig. 5 shows a modiiication 45 in which a plate is used at the upper end of the evaporator tube. Referring to Fig. l, the lower portion of the vertically arranged tube, which is intended to serve as a nlm evaporator, is marked a, the upper part intended for rectification is in- 50 dicated by ZJ. The rectication portion is provided with bubble caps located in a series of partitions c on which takes place the rectication between the sulphuric acid-water vapours streaming up from below and the sulphuric acid 55 supplied through the pipe d. Coaxially arranged in the tube'portion a. is a narrower tube e with inclined slits f passing from bottom to top to-` wards the interior, through which the sulphuric acid-water vapours pass into the interior of the tube and stream upwards with slight excess pressure. The intermediate space between the tubes a and e is provided with a filling y in small pieces. The concentrated sulphuric acid passes out at the lower end of the tube a through the outlet h, while on the other hand water vapours escape at the upper end of the tube portion h through the outlet z'. The tube portion a is located in the heating chamber k in which the fire gases enter through the opening'l and pass out through the opening m.

It has been shown that a single tube of greater length can be composed of several small tubes without the packings which are subjected to the attack both of the fire gases and also of the sulphuric acid, being injured, which was to be feared. This is due to the fact that at the pack,- ings no hydrostatic pressure prevails, since the tubes are not completely nlled with sulphuric acid but this iiows down on the interior surfaces of the tube walls.

As previously mentioned, a plate can be used at the upper end of the evaporator tube a for conducting the sulphuric `acid to the inner wall thereof. This construction is illustrated in Fig. 5, wherein the reference letter p indicates an annular plate secured to the inner tube c and sloping downward toward the evaporator tube a, from which it is separated by a narrow annular slot. The acid delivered to the space above the plate flows through the slot and down the wali of the evaporator tube.

According to Figures 2, 3 and 4, which are on a smaller scale, a large number of tubes for example with a diameter of 3D0 mm. is arranged about a generator which serves for the gasification of the combustible material necessary for the heating operation. On account of this arrangement not only is a very large heating surface attained in relatively small space, but also loss of heat by the generator by radiation into the external surroundings is avoided.

In the arrangement of for example 32 tubes each of four square metres heating surface in two annular series about a generator according to Figure 3, 128 square metres of heating surface can be brought into a unit element of 4 X e m. area at the base and 5 m. actual height with 2 m. height of the base.

If the tubes lie in the form of a horseshoe about the generator .according to Figure Lthe charging of the generator and the removal of the cinders is possible from the back instead of from the top and bottom.

I claim:

y l. In an apparatus for the concentration of sulphuric acid, a vertical tube comprising a lower tion, an outlet for water vapor at the top of the upper section, and means for withdrawing concentrated acid from the bottom of the lower section.

. 2.-In an apparatus for the concentration of sulphuric acid, a vertical tube comprising a lower evaporating section and an upper rectifrying section, means for heating the lower section, means for introducing dilute acid at the top of the rectifying section, an inner tube concentric with and spaced away from the lower section of the rst tube, the interior of the second tube communicating with the rectifying means in the first tube, means for delivering the acid to the space between said tubes when it leaves the said upper section, a iilling between said tubes for causing the acid to iiow down the tube surfaces in thin streams, openings in the wall of the second tube for the passage of vapors, an outlet for water vapor at the top of the said upper section, and means for withdrawing concentrated acid from the bottom of the said lower section.

3. In an apparatus for concentrating sulphuric acid, a vertical tube, a series of partitions in the upper section of said tube equipped with bubble caps and overflow pipes, means for introducing dilute acid at the top of the tube, a second tube concentric with and spaced away from the lower section of the first tube, the interior of the second tube communicating with the bubble cap in the lowerniost partition and the overflow pipe in said partition emptying into the space between said tubes, a filling in said space to cause the acid to flow down the tube surfaces in thin streams, means for applying heat to the lower section of the first tube, openings in the wall of the second tube for the passage of vapors, a vapor outlet at the top of the iirst tube, and means for withdrawing concentrated acid rom the bottom of the first tube.

4. Apparatus for concentrating sulphuric acid comprising a plurality of vertical tubes as claimed in claim l, and a common heating means around which the said tubes are arranged in a circular formation.

5. Apparatus for concentrating sulphuric acid comprising a plurality of vertical tubes as claimed in claim l, and a common heating means around which said tubes are arranged in a horseshoeshaped formation.

HARRY PAULING. 

